Ultrasonic imaging methods traditionally use a series of point scans called A scans arranged in a line to create a linear scan called a B scan. The A scan may involve generating a longitudinal or shear wave using a transducer and studying the received echoes. The B scans, which are slices of the imaged body may provide a 2D image of that slice of the imaged body. To create a 3D image, which may be called a C image, a series of B scans separated by a fixed distance are performed. Performing B and C scans requires that the subject of the scan be fixed (not moving) in location and the sensors are fixed on a linear track to provide stable geometry.
To convert an A-scan to a B-scan or a C-scan, a motor driven ultrasonic probe or a mechanical scanner actuated by motors or pneumatics are used, often also requiring an encoder to track the motion of the probe along the fixed track. These apparatuses are large, heavy and expensive. As such they are not portable and are unwieldy to use. The size and weight of the scanning apparatus also interferes with sensitive measurements. Alternately, other than mechanical scanning mechanisms, phased array or linear transducers may be used which have many ultrasonic transducers. However this increases the cost of the scanning apparatus and also makes it bulky.
Additionally, that the subject needs to be still throughout use is a significant limitation on the subject requiring special apparatus to hold the subject. If the apparatus is not able to hold a subject, imaging may be frustrated or not possible. For subjects that cannot be held still, such as infants or persons with certain diseases, they may have to be medicated before a scan can be performed.
Accordingly, there is a need for an improved imaging device that is less expensive, more portable and more tolerant to the movement of the subject.